1. Field of the Invention
A new improved Ziegler type catalyst system for alphaolefin type polymerization includes R'.sub.3 Y or R'.sub.2 YX and mixtures thereof, at least one Group IVB-VIII transition metal halide, and R'.sub.2 YNR.sub.2 or R'XYNR.sub.2 at a concentration level of about 0.05 to about 5.0 mole per mole of TiCl.sub.3, wherein X is a halide, R' is selected from the group consisting of C.sub.1 to C.sub.20 primary alkyl, secondary alkyl, tertiary alkyl, neopentyl alkyl, branched alkyl, naphthenic, or aralkyl groups, R is selected from the group consisting of C.sub.3 to C.sub.20 bulky alkyl, cycloalkyl aryl or substituted aryl groups, or a cyclic amine group, and Y is selected from the group consisting of aluminum, gallium or indium. The improved catalyst system provides increased polymerization activity without significantly affecting the crystallinity of the polymer because the alkyl metal compound selectively removes R'AlX.sub.2 from the surface of TiCl.sub.3 where it is believed to normally act as a poison, wherein the R'AlX.sub.2 is a by-product formed in initial catalyst manufacture and during the course of polymerization which tends to promote the formation of polymers having a low degree of crystallinity.
2. Description of the Prior Art
There is extensive art on the polymerization of ethylene and higher alpha-olefins, including dienes, using Ziegler-type catalysts containing either alkyl metals or alkyl metals in which an alkyl group has been replaced by X, OR, SR, NR.sub.2, etc., in combination with a transition metal compound of Groups IVB-VIII, where X=halide and R=C.sub.1 to C.sub.20 hydrocarbyl substituent.
For the commercial stereospecific polymerization of propylene and higher alpha olefins, only a few alkyl metal compounds have been found effective in combination with titanium or vanadium chlorides. Commercially, only R.sub.2 AlCl or R.sub.3 Al are used together with a crystalline form of TiCl.sub.3 or TiCl.sub.3.nAlCl.sub.3. Mixtures of R.sub.3 Al and R.sub.2 AlCl and RAlCl.sub.2 are made in situ and have been disclosed as catalyst components frequently in the art. R is preferably ethyl (Et) or isobutyl; n=0.01 to 0.75.
It is also well known that, in propylene polymerizations using TiCl.sub.3, catalyst activity decreases sharply in the series AlEt.sub.3, Et.sub.2 AlCl, EtAlCl.sub.2 (Malatesta, Can. J. Chem. 37. 1176 (1959) and Boldyreva et. al., Vysokomolekul. Soedin 1, 900 (1959); C.A. 55, 2454a (1961). When the chloride in Et.sub.2 AlCl is replaced by OR, SR, SeR or NR.sub.2, activity and polymer isotacticity usually drop drastically (Danusso, J. Polymer Sci. C4, 1497 (1964)).
In the present inventor's research, Et.sub.2 AlOEt and Et.sub.2 AlNEt.sub.2 were found to have some activity with TiCl.sub.3, but the polypropylene obtained was nearly atactic (Langer, Seventh Biennial Polymer Symposium, Florida, Dec. 8, 1974). Therefore, the art teaches that both activity and polymer isotacticity are extremely low when R.sub.2 AlNR.sub.2 (aluminum amide) compounds are used as replacements for conventional alkyl metal cocatalyst components.
This inventor's U.S. Pat. No. 3,418,304 discloses a complex of alkyl metal compounds such as Et.sub.2 AlNEt.sub.2 and Lewis acid salts such as AlCl.sub.3 and MgCl.sub.2, e.g., Et.sub.2 AlNEt.sub.2.AlCl.sub.3 as cocatalysts to entirely replace conventional aluminum alkyls, but such complexes are entirely different from the concept of utilizing certain metal amides as catalyst supplements for conventional Ziegler systems with Et.sub.3 Al or Et.sub.2 AlCl as cocatalysts.
U.S. Pat. No. 3,255,169 discloses a Ziegler catalyst system employing aluminum hydroaminate compounds. Typical of these is HAl(NHC.sub.2 H.sub.5).sub.2 which is used as a total substitution for the conventional aluminum alkyl cocatalyst.
Recently, U.S. Pat. No. 3,905,913 has issued disclosing the use of ##STR1## where X is H or halogen, both Rs are hydrocarbon radicals; and R' is a divalent hydrocarbon radical. These compounds are not closely related to those of the invention herein. And they are used as the sole aluminum-containing cocatalyst component.